Such electric motors are counted as belonging to the state of the art and serve for the most varied of drive purposes, for example of centrifugal pumps, compressors, stirring devices and likewise. Thereby, a control apparatus or likewise for the electric motor is arranged mostly directly on the motor housing or separately therefrom, and this control apparatus comprises a control apparatus housing or another further housing, in which at least one component producing heat on operation of the motor, for example a power resistor, a transistor, thyristor, triac or likewise, is arranged. With modern electric motors, the control apparatus often not only contains a winding commutation, but a frequency converter which renders it possible to activate the motor with practically infinite frequencies and thus rotation speeds. Such frequency converters contain power electronics which produce heat which is to be led away.
From DE 36 42 724 C2, it is counted as belonging to the state of the art to cool the further housing, and there, in particular the frequency converter housing, by way of the cooling airflow which is produced by a fan wheel seated on the motor shaft outside on the motor and which is led along the motor by way of a fan cowl. For this, the power electronics components producing heat are arranged in the region of this further housing, which is close to the ground.
Furthermore, it is counted as belonging to the state of the art to design the further housing on its outer side in a ribbed manner and to cool it by way of convection.
If is insufficient for the cooling, a separate fan can be provided outside on the housing and this fan leads the airflow into the housing in a targeted manner and thus cools it. An airflow can also be led through the housing. The arrangement of a separate, typically electromotorically driven cooling blower however has the disadvantage that it worsens the efficiency of the assembly and moreover that it represents an additional fault source and can prematurely fail.
Moreover, with pump assemblies, it is counted as belonging to the state of the art, to cool the power electronics of the frequency converter with liquid, but this per se is not so practical with electric motors.